Materials based on polylactic acid (PLA) are currently used in the manufacture of fibers or films.
Although such materials are of major interest because of their biodegradable or renewable properties, they remain little employed in a number of fields owing to their relatively poor intrinsic properties, especially mechanical properties.
In particular, the use of commercially available materials based on polylactic acid by injection molding, for the manufacture, for example, of consumer goods such as portable telephone or computer parts, requires the impact strength and the thermomechanical properties of the PLA to be improved.
To improve such properties, and in particular the impact strength, of materials based on polylactic acid, it has been proposed to use a composite obtained from a composition comprising polylactic acid (PLA) and a polyamide. However, although the impact strength of the composite is actually improved by the addition of polyamide in the composition, it has been observed that the stiffness is reduced compared with that of a material made from a composition containing no polyamide and also that the thermomechanical resistance of the composite is insufficient.
To increase the impact strength of such composites while at the same time maintaining stiffness and thermomechanical resistance, document JP 2004-051835 describes a composite obtained from a particular composition comprising 100 parts by weight of polylactic acid and 1 to 100 parts by weight of what is called a “flexible” polyamide.
The “flexible” polyamide of the composition described in JP 2004-051835 is defined as being a polyamide having a flexural modulus of elasticity at room temperature of less than 2 GPa.
However, for some applications, such as those mentioned above (consumer goods), it has been observed that the impact strength of the composite described in document JP 2004-051835 is still not entirely satisfactory.
Furthermore, the composition described in JP 2004-051835 dictates a particular choice of polyamide, which may have a drawback, for example in terms of cost.
The object of the present invention is therefore to remedy the aforementioned drawbacks and to propose a composite that has an improved impact strength while still maintaining stiffness and thermomechanical resistance, especially one that is compatible with a method of manufacture by injection molding.